Velocity saturation – Mobility degradation – body effect – CLM CMOS by VLSI Universe - May 5, 2020July 21, 20210 The non-ideal current-voltage effects such as velocity saturation, mobility degradation, body effect, and the channel length modulation CLM are explained. Velocity Saturation At the high lateral electric field Elat that is equal to Vds/L, the velocity of the carrier ceases to increase linearly with the field strength is called Velocity saturation. The velocity saturation results in lower Ids that which is expected at High Vds. Mobility Degradation At high vertical field strengths Evert that is equal to Vgs/tox, the carriers scatter in the oxide SiO2 interface and the process gets slower is called Mobility degradation. Mobility degradation also reduces the current Ids that are expected at high Vgs. Channel length modulation CLM The saturation current Isat of the non-ideal transistor increases with Vds, which is mainly caused by
Threshold Voltage | VTCMOS | Body bias CMOS by VLSI Universe - April 21, 2020July 20, 20210 The main role of VTCMOS, threshold voltage of CMOS, body bias method in the static power reduction techniques is explained. The main role of the body bias method in the static power reduction techniques The threshold voltage Vth can be defined as the gate voltage Vg when the inversion with a density similar to that of the concentration of substrate starts at an oxide SiO2 interface in a CMOS device. When the gate voltage Vg is not enough to reach threshold voltage Vth, the width W of the depletion region under the gate is a function of the gate voltage Vg. Threshold voltage dependence on substrate doping density 1. The threshold voltage Vth is less sensitive to the doping density of the substrate when the
CMOS Inverter | VTC | Noise Margin June 2021 CMOS by VLSI Universe - April 21, 2020July 20, 20210 One of the main advantages of the CMOS inverter is it consumes power only during the transients/operation. At the steady-state, it consumes no power. The difference between hole mobility and electron mobility can be compensated and make tphl and tplh, rise, and fall delays more compatible by designing or adjusting the width by length W/L ratios of the PMOS and NMOS devices. The symmetric tphl and tplh, rise and fall delays facilitate the very easy circuit design. In CMOS inverter the input-output I/O transfer curve can be symmetric wrt. (with respect to) the center of the signal swing so that the NM noise margin can be optimized here. The load capacitance CL can be reduced by scaling. And by increasing the width by
